AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin

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Predicting Plays in the Frontier Rockall Basin: Why Analogues Matter

Abstract

Discoveries such as Dooish and Benbecula in the Irish and UK sectors of the Rockall Basin and successful petroleum provinces offshore Norway and in the Faroe-Shetland Basin, highlight the exploration potential of the underexplored frontier Rockall Basin. Paleogene volcanics in the northern Rockall Basin can make the interpretation of underlying stratigraphy challenging, especially as stratigraphic constraint is restricted to a small number of wells on the basin margins. Within these wells, some key stratigraphic intervals of exploration significance are not preserved or are not penetrated. Therefore, predicting the pre-volcanic structure and stratigraphy of the Rockall Basin relies on a thorough understanding of the early Permo-Triassic rift history and subsequent North Atlantic rift events. The petroleum systems elements prediction has been enhanced using insights gained from wells in the perched margin basins offshore Ireland, such as Slyne and Erris, and from the Faroe-Shetland Basin. Significant reservoir intervals include Late Carboniferous-Middle Jurassic clastics, which are a proven reservoir in the Dooish discovery in the southern Rockall Basin, and there could be analogous plays elsewhere in the basin. The potential for Late Jurassic sandstones sourced from the Erris Ridge, similar to those of the Late Jurassic Rona Member in the Faroe-Shetland Basin sourced from the Rona Ridge, has also been identified. Untested Cretaceous turbidite plays have also been the subject of exploration interest in the Rockall Basin. Cretaceous stratigraphy in the deeper basin is poorly understood, but reservoir and play potential can be evaluated considering the tectonic context (Cretaceous rifting) and potential analogues (turbidite sandstones of the Commodore Formation in the Faroe-Shetland Basin and the Aasta Hansteen Field in the Vøring Basin). Paleocene deepwater sandstones are a proven reservoir in the Benbecula discovery in the northern Rockall Basin. The potential for similar plays elsewhere in the basin, for intrabasalt clastic plays analogous to the Rosebank play in the Faroe-Shetland Basin, and the potential for post-volcanic Eocene deepwater turbidite plays have been evaluated. The 2015 OGA seismic dataset has been integrated in the northern Rockall Basin to identify potentially significant seismic features, such as updip pinchouts or channel systems, and changes in seismic character, suggesting lithological variations. The key exploration risk for post-volcanic plays in the northern Rockall Basin is reservoir quality. Evaluating the potential for fluvial systems reworking sediment from a non-volcanic provenance can provide insight on this aspect of reservoir risk. On the basis of the discoveries in the basin to date and a diverse range of untested plays, many analogous to producing plays in neighboring basins, the Rockall Basin will be of interest for future hydrocarbon exploration.